Early A Trunk Quarter Panel "Abyss"

On my 76 Aspen I user rigid foam insulation board. You know the foil faced stuff.Used 1 in thick stuff and cut it to a tight fit then caulked it around the edges . Got tired of loosing things thru the rusted out quarters. It worked real well and actually looks decent when I open the trunk. Also stopped the problem of my brake lights taking a crap from water and road salt in winter .